U.S. patent application number 12/055621 was filed with the patent office on 2008-08-07 for method of polishing a substrate.
Invention is credited to Chau H. Duong.
Application Number | 20080188163 12/055621 |
Document ID | / |
Family ID | 37776011 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080188163 |
Kind Code |
A1 |
Duong; Chau H. |
August 7, 2008 |
Method of polishing a substrate
Abstract
A method for polishing a substrate using a pad comprising, a
polymeric matrix having microspheres dispersed therein, the
polymeric matrix being formed of a water-based polymer or blends
thereof, wherein the polymeric matrix is applied on a permeable
substrate, and wherein the polishing pad exhibits reduced
defectivity and improved polishing performance are provided.
Inventors: |
Duong; Chau H.; (Newark,
DE) |
Correspondence
Address: |
ROHM AND HAAS ELECTRONIC MATERIALS;CMP HOLDINGS, INC.
451 BELLEVUE ROAD
NEWARK
DE
19713
US
|
Family ID: |
37776011 |
Appl. No.: |
12/055621 |
Filed: |
April 23, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11504415 |
Aug 14, 2006 |
|
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12055621 |
|
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60718489 |
Sep 19, 2005 |
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Current U.S.
Class: |
451/36 |
Current CPC
Class: |
B24B 37/24 20130101;
C08L 2666/04 20130101; C08K 7/22 20130101; C08L 75/04 20130101;
C08L 75/04 20130101; C08L 33/06 20130101 |
Class at
Publication: |
451/36 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Claims
1. A chemical mechanical planarization method comprising: providing
a chemical mechanical polishing pad comprising, a permeable
substrate having a thickness of 2-100 mils; and a polishing layer
comprising a polymeric matrix having microspheres dispersed
therein, wherein the polymeric matrix is formed of a water-based
polymer blend, wherein the polishing layer is applied on the
permeable substrate, wherein the polymeric matrix comprises a blend
of 3:1 to 1:3 (by weight) of an aqueous urethane dispersion and an
acrylic dispersion, wherein the microspheres are gas filled,
wherein the polymeric matrix contains at least 0.3 volume percent
microspheres, wherein the microspheres have a weight average
diameter of 10-100 .mu.m, wherein the polishing layer has grooves
formed therein; and, wherein the chemical mechanical polishing pad
exhibits improved defectivity.
2. The method of claim 1, wherein the polymeric matrix penetrates
and binds to the permeable substrate.
3. The method of claim 1, wherein the permeable substrate is a
woven or a non-woven web.
4. The method of claim 1, wherein the polymeric matrix comprises a
blend of 3:1 (by weight) of an aqueous urethane dispersion and an
acrylic dispersion.
5. A chemical mechanical planarization method comprising: providing
a chemical mechanical polishing pad comprising, a permeable
substrate having a thickness of 2-100 mils; and a polishing layer
comprising a polymeric matrix having microspheres dispersed
therein, wherein the polymeric matrix is formed of a water-based
polymer blend, wherein the polishing layer is applied on the
permeable substrate, wherein the polymeric matrix comprises a blend
of 3:1 to 1:3 (by weight) of an aqueous urethane dispersion and an
acrylic dispersion, wherein the microspheres are gas filled,
wherein the polymeric matrix contains at least 0.3 volume percent
microspheres, wherein the microspheres have a weight average
diameter of 10-100 .mu.m, wherein the polishing layer has grooves
formed therein; and, wherein the chemical mechanical polishing pad
exhibits improved defectivity, where the chemical mechanical
polishing pad creates less than 300 total defects on the surface of
a copper sheet wafer when the chemical mechanical polishing pad is
used to polish the copper sheet wafer on a polishing machine, under
downforce conditions of 1.5 psi, a polishing solution flow rate of
150 cc/min, a platen speed of 120 RPM and a carrier speed of 114
RPM to polish copper sheet wafers.
6. The method of claim 5, wherein the wherein the polymeric matrix
comprises a blend of 3:1 (by weight) of an aqueous urethane
dispersion and an acrylic dispersion.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application of U.S. application Ser.
No. 11/504,415, filed Aug. 14, 2006, which claims the claims the
benefit of U.S. Provisional Application Ser. No. 60/718,489 filed
Sep. 19, 2005.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to methods of using polishing
pads for chemical mechanical planarization (CMP), and in
particular, relates to methods of using water-based polishing pads
exhibiting improved defectivity.
[0003] In the fabrication of integrated circuits and other
electronic devices, multiple layers of conducting, semiconducting
and dielectric materials are deposited on or removed from a surface
of a semiconductor wafer. Thin layers of conducting,
semiconducting, and dielectric materials may be deposited by a
number of deposition techniques. Common deposition techniques in
modern processing include physical vapor deposition (PVD), also
known as sputtering, chemical vapor deposition (CVD),
plasma-enhanced chemical vapor deposition (PECVD), and
electrochemical plating (ECP).
[0004] As layers of materials are sequentially deposited and
removed, the uppermost surface of the wafer becomes non-planar.
Because subsequent semiconductor processing (e.g., metallization)
requires the wafer to have a flat surface, the wafer needs to be
planarized. Planarization is useful in removing undesired surface
topography and surface defects, such as rough surfaces,
agglomerated materials, crystal lattice damage, scratches, and
contaminated layers or materials.
[0005] Chemical mechanical planarization, or chemical mechanical
polishing (CMP), is a common technique used to planarize
substrates, such as semiconductor wafers. In conventional CMP, a
wafer carrier is mounted on a carrier assembly and positioned in
contact with a polishing pad in a CMP apparatus. The carrier
assembly provides a controllable pressure to the wafer, pressing it
against the polishing pad. The pad is moved (e.g., rotated)
relative to the wafer by an external driving force. Simultaneously
therewith, a chemical composition ("slurry") or other fluid medium
is flowed onto the polishing pad and into the gap between the wafer
and the polishing pad. Thus, the wafer surface is polished and made
planar by the chemical and mechanical action of the slurry and pad
surface.
[0006] Casting polymers (e.g., polyurethane) into cakes and cutting
("skiving") the cakes into several thin polishing pads has proven
to be an effective method for manufacturing "hard" polishing pads
with consistent reproducible polishing properties. Unfortunately,
polyurethane pads produced from the casting and skiving method can
have polishing variations arising from a polishing pad's casting
location. For example, pads cut from a bottom casting location and
a top casting can have different densities and porosities.
Furthermore, polishing pads cut from molds of excessive size can
have center-to-edge variations in density and porosity within a
pad. These variations can adversely affect polishing for the most
demanding applications, such as low k patterned wafers.
[0007] Also, coagulating polymers utilizing a solvent/non-solvent
process to form polishing pads in a web format has proven to be an
effective method of manufacturing "soft" polishing pads. This
method (i.e., web-format) obviates some of the drawbacks discussed
above that is found in the casting and skiving process.
Unfortunately, the (organic) solvent that is typically used (e.g.,
N,N-dimethyl formamide) may be cumbersome and cost prohibitive to
handle. In addition, these soft pads may suffer from pad-to-pad
variations due to the random placement and structure of the
porosities that are formed during the coagulation process.
[0008] In addition, polishing pads may be formed by combining two
or more pads together. For example, Rutherford et al., in U.S. Pat.
No. 6,007,407, discloses polishing pads for performing CMP that are
formed by laminating two layers of different materials. The upper
polishing layer is attached to a lower layer or "sub-pad" formed
from a material suitable for supporting the polishing layer. The
sub-pad typically has higher compressibility and lower stiffness
than the polishing layer and essentially acts as supporting
"cushions" for the polishing layer. Conventionally, the two layers
are bonded with a pressure-sensitive adhesive ("PSA"). However,
PSAs have relatively low bonding strength and marginal chemical
resistance. Consequently, a laminated polishing pad utilizing PSAs
tend to cause the sub-pad to separate ("delaminate") from the upper
polishing layer, or vice versa, during polishing, rendering the pad
useless and impeding the polishing process.
[0009] Thus, there is a demand for a polishing pad with improved
density and porosity uniformity. In particular, what is needed is a
polishing pad that provides consistent polishing performance, lower
defectivity, which resists delamination and is cost effective to
manufacture.
STATEMENT OF THE INVENTION
[0010] In a first aspect of the present invention, there is
provided a chemical mechanical polishing pad comprising, a
polymeric matrix having microspheres dispersed therein, the
polymeric matrix being formed of a water-based polymer or blends
thereof, and wherein the polymeric matrix is applied on a permeable
substrate.
[0011] In a second aspect of the present invention, there is
provided a chemical mechanical polishing pad comprising, a
polymeric matrix having porosity or filler dispersed therein, the
polymeric matrix being formed of a blend of a urethane and acrylic
dispersion at a ratio by weight percent of 100:1 to 1:100, and
wherein the polymeric matrix is applied on a permeable
substrate.
[0012] In a third aspect of the present invention, there is
provided a method of manufacturing a chemical mechanical polishing
pad, comprising: supplying a water-based fluid phase polymer
composition containing microspheres onto a continuous transported
permeable substrate; shaping the polymer composition on the
transported permeable substrate into a fluid phase polishing layer
having a predetermined thickness; curing the polymer composition on
the transported permeable substrate in a curing oven to convert the
polymer composition to a solid phase polishing layer of the
polishing pad.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates an apparatus for continuous manufacturing
of the water-based polishing pad of the present invention;
[0014] FIG. 1A illustrates another manufacturing apparatus of the
present invention;
[0015] FIG. 2 illustrates an apparatus for continuous conditioning
of the water-based polishing pad of the present invention;
[0016] FIG. 3 illustrates a cross section of the water-based
polishing pad manufactured according to the apparatus disclosed by
FIG. 1;
[0017] FIG. 3A illustrates another water-based polishing pad
manufactured according to the apparatus disclosed by FIG. 1;
and
[0018] FIG. 3B illustrates another water-based polishing pad
manufactured according to the apparatus disclosed by FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention provides a water-based polishing pad
with reduced defectivity and improved polishing performance.
Preferably, the polishing pad is manufactured in a web-format and
reduces the pad-to-pad variations often associated with cast and
skived "hard" polishing pads. In addition, the polishing pad is
preferably water-based rather than organic-solvent based, and
easier to manufacture than prior art "soft" pads formed by a
coagulation process. Also, the polishing pad is directly applied to
a permeable substrate, eliminating the use of adhesives, and
decreasing cost and delamination of the polishing pad. The
polishing pad of the present invention is useful for polishing
semiconductor substrates, rigid memory disks, optical products and
for use in polishing various aspects of semiconductor processing,
for example, ILD, STI, tungsten, copper, low-k dielectrics and
ultra low-k dielectrics.
[0020] Referring now to the drawings, FIG. 1 discloses an apparatus
100 for manufacturing a water-based polishing pad 300 of the
present invention. Preferably, the water-based polishing pad 300 is
formed in a "rolled" format that allows "continuous manufacturing"
to reduce variations among different polishing pads 300 that may be
caused by batch processing. The apparatus 100 includes a feed reel
or an unwind station 102 that stores a helically-wrapped permeable
substrate 302 in lengthwise continuous form. The substrate 302 is
formed of any permeable membrane, such as, a woven or non-woven
web, for example, spun-bonded web or needle-punched web (e.g., Suba
IV.TM. from Rohm and Haas Electronic Materials CMP Inc., of Newark,
Del.). In the present invention, the substrate 302 preferable
becomes an integral part of the final product. Any material,
including, polyester, nylon and other fibers, including blends
thereof, can be used to form the permeable substrate 302. As
discussed below, at least some of the viscous, fluid state polymer
composition penetrates and binds to the permeable membrane of the
substrate 302, which allows improved chemical and mechanical
adhesion properties over conventional adhesive techniques.
[0021] The substrate 302 preferably has a thickness between 2 mils
to 100 mils (0.051 mm to 2.54 mm). More preferably, the substrate
302 preferably has a thickness between 10 mils to 60 mils (0.254 mm
to 1.52 mm). Most preferably, the substrate 302 preferably has a
thickness between 20 mils to 30 mils (0.508 mm to 0.762 mm).
[0022] The feed roller 102 is mechanically driven to rotate at a
controlled speed by a drive mechanism 104. The drive mechanism 104
includes, for example, a belt 106 and motor drive pulley 108.
Optionally, the drive mechanism 104 includes, a motor driven
flexible shaft or a motor driven gear train (not shown).
[0023] Referring still to FIG. 1, the continuous substrate 302 is
supplied by the feed reel 102 onto a continuous conveyor 110, for
example, a stainless steel belt, that is looped over spaced apart
drive rollers 112. The drive rollers 112 may be motor driven at a
speed that synchronizes linear travel of the conveyor 110 with that
of the continuous substrate 302. The substrate 302 is transported
by the conveyor 110 along a space between each drive roller 112 and
a corresponding idler roller 112a. The idler roller 112a engages
the conveyor 110 for positive tracking control of the substrate
302. The conveyor 110 has a flat section 110a supported on a flat
and level surface of a table support 110b, which supports the
substrate 302 and transports the substrate 302 through successive
manufacturing stations 114, 122 and 126. Support members 110c in
the form of rollers are distributed along the lateral edges of the
conveyor 110 and the substrate 302 for positive tracking control of
the conveyor 110 and the substrate 302.
[0024] The first manufacturing station 114 further including a
storage tank 116 and a nozzle 118 at an outlet of the tank 116. A
viscous, fluid state polymer composition is supplied to the tank
116, and is dispensed by the nozzle 118 onto the continuous
permeable substrate 302. The flow rate of the nozzle 118 is
controlled by a pump 120 at the outlet of the tank 116. The nozzle
118 may be as wide as the width of the continuous permeable
substrate 302 to cover the entirety of substrate 302. As the
conveyor 110 transports the continuous permeable substrate 302 past
the manufacturing station 114, a continuous-fluid phase polishing
layer 304 is supplied onto the substrate 302. In this way, at least
some of the viscous, fluid state polymer composition penetrates and
binds to the permeable membrane of the substrate 302, which allows
improved chemical and mechanical adhesion properties over
conventional adhesive techniques (i.e., adhering a top pad to a
sub-pad utilizing a pressure-sensitive adhesive).
[0025] Because the raw materials can be mixed in a large
homogeneous supply that repeatedly fills the tank 116, variations
in composition and properties of the finished product are reduced.
In other words, the present invention provides a web-format method
of manufacturing a water-based polishing pad to overcome the
problems with prior art cast and skive techniques. The continuous
nature of the process enables precise control for manufacturing a
water-based polishing pad 300 from, which large numbers of
individual polishing pads 300 are cut to a desired area pattern and
size. The large numbers of individual polishing pads 300 have
reduced variations in composition and properties.
[0026] Preferably, the fluid state polymer composition is
water-based. For example, the composition may comprise a
water-based urethane dispersion (e.g., W-290H, W-293, W-320, W-612
and A-100 from Crompton Corp. of Middlebury, Conn. and HP-1035 and
HP-5035 from Cytec Industries Inc. of West Paterson, N.J.) and
acrylic dispersion (e.g., Rhoplex.RTM. E-358 from Rohm and Haas Co.
of Philadelphia, Pa.). In addition, blends, such as,
acrylic/styrene dispersions (e.g., Rhoplex.RTM. B-959 and E-693
from Rohm and Haas Co. of Philadelphia, Pa.) may be utilized. In
addition, blends of the water-based urethane and acrylic
dispersions may be utilized.
[0027] In a preferred embodiment of the invention, a blend of the
water-based urethane and acrylic dispersion is provided at a ratio
by weight percent of 100:1 to 1:100. More preferably, a blend of
the water-based urethane and acrylic dispersion is provided at a
ratio by weight percent of 10:1 to 1:10. Most preferably, a blend
of the water-based urethane and acrylic dispersion is provided at a
ratio by weight percent of 3:1 to 1:3.
[0028] The water-based polymer is effective for forming porous and
filled polishing pads. For purposes of this specification, filler
for polishing pads include solid particles that dislodge or
dissolve during polishing, and liquid-filled particles or spheres.
For purposes of this specification, porosity includes gas-filled
particles, gas-filled spheres and voids formed from other means,
such as mechanically frothing gas into a viscous system, injecting
gas into the polyurethane melt, introducing gas in situ using a
chemical reaction with gaseous product, or decreasing pressure to
cause dissolved gas to form bubbles.
[0029] Optionally, the fluid state polymer composition may contain
other additives, including, a defoamer (e.g., Foamaster.RTM. 111
from Cognis) and reology modifiers (e.g., Acrysol.RTM. ASE-60,
Acrysol I-62, Acrysol RM-12W, Acrysol RM-825 and Acrysol RM-8W all
from Rohm and Haas Company. Other additives, for example, an
anti-skinning agent (e.g., Borchi-Nox.RTM. C3 and Borchi-Nox M2
from Lanxess Corp.) and a coalescent agent (e.g., Texanol.RTM.
Ester alcohol from Eastman Chemicals) may be utilized.
[0030] A second manufacturing station 122 includes, for example, a
doctor blade 124 located at a predetermined distance from the
continuous substrate 302 defining a clearance space therebetween.
As the conveyor 110 transports the continuous substrate 302 and the
fluid phase polishing layer 304 past the doctor blade 124 of the
manufacturing station 122, the doctor blade 124 continuously shapes
the fluid phase polishing layer 304 to a predetermined
thickness.
[0031] A third manufacturing station 126 includes a curing oven
128, for example, a heated tunnel that transports the continuous
substrate 302 and the polishing layer 304. The oven 128 cures the
fluid phase polishing layer 304 to a continuous, solid phase
polishing layer 304 that adheres to the continuous substrate 302.
The water should be removed slowly to avoid, for example, surface
blisters. The cure time is controlled by temperature and the speed
of transport through the oven 128. The oven 128 may be fuel fired
or electrically fired, using either radiant heating or forced
convection heating, or both.
[0032] Preferably, the temperature of the oven 128 may be between
50.degree. C. to 150.degree. C. More preferably, the temperature of
the oven 128 may be between 55.degree. C. to 130.degree. C. Most
preferably, the temperature of the oven 128 may be between
60.degree. C. to 120.degree. C. In addition, the polishing layer
304 may be moved through the oven 128 at a speed of 5 fpm to 20 fpm
(1.52 mps to 6.10 mps). Preferably, the polishing layer 304 may be
moved through the oven 128 at a speed of 5.5 fpm to 15 fpm (1.68
mps to 4.57 mps). More preferably, the polishing layer 304 may be
moved through the oven 128 at a speed of 6 fpm to 12 fpm (1.83 mps
to 3.66 mps).
[0033] Referring now to FIG. 1A, upon exiting the oven 128, the
continuous substrate 302 is adhered to a continuous, solid phase
polishing layer 304 to comprise, a continuous, water-based
polishing pad 300. The water-based polishing pad 300 is rolled
helically onto a take up reel 130, which successively follows the
manufacturing station 126. The take up reel 130 is driven by a
second drive mechanism 104. The take up reel 130 and second drive
mechanism 104 comprise, a separate manufacturing station that is
selectively positioned in the manufacturing apparatus 100.
[0034] Referring now to FIG. 2, an apparatus 200 for surface
conditioning or surface finishing of the continuous, water-based
polishing pad 300 is optionally provided. The apparatus 200
includes either a similar conveyor 110 as that disclosed by FIG. 1,
or a lengthened section of the same conveyor 110. The conveyor 110
of apparatus 200 has a drive roller 112, and a flat section 110a
supporting the water-based polishing pad 300 that has exited the
oven 126. The conveyor 110 of apparatus 200 transports the
continuous polishing pad 300 through one or more manufacturing
stations 201, 208 and 212, where the water-based polishing pad 300
is further processed subsequent to curing in the oven 126. The
apparatus 200 is disclosed with additional flat table supports 110b
and additional support members 110c, which operate as disclosed
with reference to FIG. 1.
[0035] The solidified polishing layer 304 may be buffed to expose a
desired surface finish and planar surface level of the polishing
layer 304. Asperities in the form of grooves or other indentations,
are worked into the surface of the polishing layer 304, as desired.
For example, a work station 201 includes a pair of compression
forming, stamping dies having a reciprocating stamping die 202 and
a fixed die 204 that close toward each other during a stamping
operation. The reciprocating die 202 faces toward the surface of
the continuous polishing layer 304. Multiple teeth 205 on the die
202 penetrate the surface of the continuous polishing layer 304.
The stamping operation provides a surface finishing operation. For
example, the teeth 205 indents a pattern of grooves in the surface
of the polishing layer 304. The conveyor 110 may be intermittently
paused, and becomes stationary when the dies 202 and 204 close
toward each other. Alternatively, the dies 202 and 204 move in
synchronization with the conveyor 110 in the direction of transport
during the time when the dies 202 and 204 close toward each
other.
[0036] Manufacturing station 208 includes, for example, a rotary
saw 210 for cutting grooves in the surface of the continuous
polishing layer 304. The saw 210 is moved by, for example, a
orthogonal motion plotter along a predetermined path to cut the
grooves in a desired pattern of grooves. Another manufacturing
station 212 includes a rotating milling head 214 for buffing or
milling the surface of the continuous polishing layer 304 to a
flat, planar surface with a desired surface finish that is
selectively roughened or smoothed.
[0037] The sequence of the manufacturing stations 202, 210 and 212
can vary from the sequence as disclosed by FIG. 2. One or more of
the manufacturing stations 202, 210 and 212 can be eliminated as
desired. The take up reel 130 and second drive mechanism 104
comprise, a separate manufacturing station that is selectively
positioned in the manufacturing apparatus 200 at the end of the
conveyor 110 to gather the solid phase continuous polishing pad
300.
[0038] Referring now to FIG. 3, a sectional view of the polishing
pad 300 manufactured by the apparatus 100 of the present invention
is provided. As discussed above, upon curing in the oven 128, the
water-based polymer forms a solidified, continuous polishing pad
300. Optionally, the polishing pad 300 may comprise abrasive
particles or particulates 306 in the polishing layer 304 to form a
fixed-abrasive pad. Accordingly, the abrasive particles or
particulates 306 are included as a constituent in the fluid state
polymer mixture. The polymer mixture becomes a matrix that is
entrained with the abrasive particles or particulates 306.
[0039] Referring now to FIG. 3A, in another embodiment of the
polishing pad 300 of the present invention, an entrained
constituent in the form of, a foaming agent or blowing agent or a
gas, is included in the polymer mixture, which serves as a matrix
that is entrained with the constituent. Upon curing, the foaming
agent or blowing agent or gas escapes as volatiles to provide the
open pores 308 distributed throughout the continuous polishing
layer 304. Polishing pad 300 of FIG. 3A further comprises the
substrate 302.
[0040] Referring now to FIG. 3B, another embodiment of the
polishing pad 300 is disclosed, comprising microballons or
polymeric microspheres 310 included in the polymer mixture, and
distributed throughout the continuous polishing layer 304. The
microspheres 310 may be gas filled. Alternatively the microspheres
310 are filled with a polishing fluid that is dispensed when the
microspheres 310 are opened by abrasion when the polishing pad 300
is used during a polishing operation. Alternatively, the
microspheres 310 are water soluble polymeric microelements that are
dissolved in water during a polishing operation. Polishing pad 300
of FIG. 3B further comprises the substrate 302.
[0041] Preferably, at least a portion of the microspheres 310 are
generally flexible. Suitable microspheres 310 include inorganic
salts, sugars and water-soluble particles. Examples of such
polymeric microspheres 310 (or microelements) include polyvinyl
alcohols, pectin, polyvinyl pyrrolidone, hydroxyethylcellulose,
methylcellulose, hydropropylmethylcellulose,
carboxymethylcellulose, hydroxypropylcellulose, polyacrylic acids,
polyacrylamides, polyethylene glycols, polyhydroxyetheracrylites,
starches, maleic acid copolymers, polyethylene oxide,
polyurethanes, cyclodextrin and combinations thereof. The
microspheres 310 may be chemically modified to change the
solubility, swelling and other properties by branching, blocking,
and crosslinking, for example. A preferred material for the
microsphere is a copolymer of polyacrylonitrile and polyvinylidene
chloride (e.g., Expancel.TM. from Akzo Nobel of Sundsvall,
Sweden).
[0042] Preferably, the water-based polishing pads 300 may contain a
porosity or filler concentration of at least 0.3 volume percent.
This porosity or filler contributes to the polishing pad's ability
to transfer polishing fluids during polishing. More preferably, the
polishing pad has a porosity or filler concentration of 0.55 to 70
volume percent. Most preferably, the polishing pad has a porosity
or filler concentration of 0.6 to 60 volume percent. Preferably the
pores or filler particles have a weight average diameter of 10 to
100 .mu.m. Most preferably, the pores or filler particles have a
weight average diameter of 15 to 90 .mu.m. The nominal range of
expanded hollow-polymeric microspheres' weight average diameters is
15 to 50 .mu.m.
[0043] Accordingly, the present invention provides a water-based
polishing pad with reduced defectivity and improved polishing
performance. Preferably, the polishing pad is manufactured in a
web-format and reduces the pad-to-pad variations often associated
with cast and skived "hard" polishing pads. In addition, the
polishing pad is preferably water-based rather than organic-solvent
based, and has a greater yield and less defects than prior art
"soft" pads formed by a coagulation process. Also, at least some of
the viscous, fluid state polymer composition penetrates and binds
to the permeable membrane of the substrate, which allows improved
chemical and mechanical adhesion properties over conventional
adhesive techniques.
EXAMPLES
[0044] The following Table illustrates the improved defectivity of
the water-based pad of the present invention. The water-based pad
was formed by mixing 75 grams of W-290H urethane dispersion from
Crompton Corp. with 25 grams of Rhoplex.RTM. E-358 acrylic
dispersion from Rohm and Haas Company in a 3 to 1 ratio for 2
minutes in a mix tank. Then, 1 gram of Foamaster.RTM. 111 defoamer
from Cognis was added to the mix tank and mixed for another 2
minutes. Then 0.923 grams of Expancel.RTM. 551 DE40d42
(Expancel.RTM. 551DE40d42 is a 30-50 .mu.m weight average diameter
hollow-polymeric microsphere manufactured by Akzo Nobel) was added
to the mix tank and mixed for another 5 minutes. Also, 1 gram of a
thickener, Acrysol.RTM. ASE-60 and 5 Acrysol I-62, both from Rohm
and Haas Company was added to the mix tank and mix for 15 minutes.
Then, the mixture was coated (50 mils (1.27 mm) thick wet) on a
Suba IV.TM. permeable substrate and dried in a hot air oven at
60.degree. C. for 4 hrs. The resulting polishing pad was 25 mils
(0.64 mm) thick. The water-based polishing pad was then provided
with a circular groove having a pitch of 120 mils (3.05 mm), depth
of 9 mils (0.23 mm) and width of 20 mils (0.51 mm). An Applied
Materials Mirra.RTM. polishing machine using the water-based
polishing pad of the present invention, under downforce conditions
of 1.5 psi (10.34 kPa) and a polishing solution flow rate of 150
cc/min, a platen speed of 120 RPM and a carrier speed of 114 RPM
planarized the samples (copper sheet wafers). As shown in the
following Tables, Tests 1 to 3 represent samples polished with the
polishing pads of the present invention and Tests A1 to B2
represent comparative examples of samples polished with a prior art
pads. Namely, Test A was run with Politex.RTM. polishing pads and
Test B was run with IC 1100.RTM. polishing pads.
TABLE-US-00001 TABLE 1 Test Scratch.sup.1 Basic.sup.2 New
Basic.sup.3 1 32 162 289 2 21 105 184 A1 142 482 2989 A2 116 511
3103 B1 8136 26408 25181 B2 7885 25912 24948 .sup.1A spherical mark
on surface approximately 1-10 .mu.m in size .sup.2The Scratch
defect counts plus, a consecutive series of pits or gouges arranged
in a line approximately greater than 10 .mu.m in length.
.sup.3Includes every type of defect on a wafer.
[0045] As shown in Table 1 above, the water-based pad of the
present invention provided the least amount of defectivity in the
samples polished. For example, the samples polished with the
water-based pad of the present invention provided a greater than 10
fold decrease in defectivity as compared to the samples polished
with the prior art pads.
[0046] Accordingly, the present invention provides a water-based
polishing pad with reduced defectivity and improved polishing
performance. Preferably, the polishing pad is manufactured in a
web-format and reduces the pad-to-pad variations often associated
with cast and skived "hard" polishing pads. In addition, the
polishing pad is preferably water-based rather than organic-solvent
based, and has a greater yield and less defects than prior art
"soft" pads formed by a coagulation process. Also, the polishing
pad is directly applied to a permeable substrate, eliminating the
use of adhesives, thereby decreasing cost and exposure to
delamination of the polishing pad.
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